Gemini Surfactant-Directed Facile Pillaring of Two-Dimensional Zeolites with Enhanced Catalytic Activity in Friedel–Crafts Alkylation

Abstract

We report an efficient procedure for the synthesis of pillared MWW zeolites (MCM-36) via integrating intercalation and hydrolysis of tetraethyl orthosilicate (TEOS) into one step. Specifically, two specially selected surfactants with more hydrophilicity instead of the conventional swelling agent cetyltrimethylammonium bromide (CTAB) were employed to increase the interlayer wetting ability and water content. The resultant intercalation and hydrolysis of TEOS occur concurrently in a confined interlayer microenvironment with enriched interlayer water and basic hexamethyleneimine (HMI). It is found that the wetting ability of swelling surfactants has a profound effect on pillarization efficiency, resulting in the different degrees of order of the layered structure, pore-size distribution, and accessibility of the acid sites of MCM-36. MCM-36 prepared using a gemini-type surfactant as a swelling agent shows a highly long-range ordered structure and enhanced catalytic activity for alkylation of benzene with benzyl alcohol compared to the one produced using conventional CTAB as a swelling agent.